The present invention relates generally to a superconductor, and in particular to a system and method for quench protection of a superconductor.
A superconductor is an element, inter-metallic alloy, or compound that will conduct electricity without resistance when cooled below a critical temperature. Superconductivity occurs in a wide variety of materials, including elements such as tin and aluminum, various metallic alloys, some heavily doped semiconductors, and certain ceramic compounds. In conventional superconductors, superconductivity is caused by a force of attraction between certain conduction electrons arising from the exchange of phonons, which causes the fluid of conduction electrons to exhibit a super fluid phase composed of correlated pairs of electrons.
Superconductors are useful in a variety of applications including magnetic resonance imaging systems and power generation systems, such as motors and generators. The loss of electrical resistance in the superconductor enables these devices to be operated with a much greater efficiency. However, a portion of the superconductor undergoes a transition from the superconducting state to a normal resistive state when the current in the superconductor is driven beyond a critical current limit. This causes the temperature of the superconductor to rise due to heat produced by the resistive heating occurring in the superconductor. If this resistive heating loss continues, the superconductor may enter a state of irreversible thermal runaway, known as a quench. Damage may be caused to the superconductor due to the thermal runaway. For example, in a superconductive rotor coil, an excessive temperature gradient may be generated as a result of resistive heating. The temperature gradient may cause differential thermal expansion across the superconductive coil that damages the superconductive coil. The superconductor and/or insulation may also be damaged by excessive temperature reached during a quench.
Accordingly, a technique that enables a quench condition of the superconductor to be detected is desirable. In addition, a technique that enables the superconductor to be protected from damage that may be caused by quenching is also desirable.